To paraphrase Mark Twain, reports of the death of cold fusion are somewhat premature--at least according to its proponents.
Just over a year ago, University of Utah electrochemists B. Stanley Pons and Martin Fleischmann announced to a stunned world that they had discovered a simple desktop reaction, carried out at room temperatures, that produced energy in the same way as the fiery furnace of the sun. When they applied a small electric current to platinum and palladium electrodes immersed in deuterium oxide, a "heavy" form of water, they said, deuterium atoms fused together, forming helium atoms and releasing large amounts of energy.
Their announcement promised something that researchers have been dreaming of and seeking for decades--an inexpensive source of energy that is produced from highly abundant materials and that produces no polluting byproducts.
But despite subsequent reports of partial successes elsewhere, most chemists and physicists around the world were unsuccessful in their hurried efforts to reproduce the unexpected results. And, within four months, the unorthodox concept had seemingly been relegated to the dustbin of history.
At the end of March, however, more than 200 staunch advocates of cold fusion from the United States, Italy, Japan, India and Taiwan gathered here for the First Annual Conference on Cold Fusion to compare notes on their research, to encourage one another in their lonely quest and generally to shout their defiance of the physics community at large.
The physics community, for its part, took little public notice of the affair--except for Robert Parks of the American Physical Society, who derisively termed the meeting a "seance of true believers."
That community also sent a handful of self-appointed "skeptics-at-large," most notably Stephen Kellogg of Caltech, Richard Petrasso of the Massachusetts Institute of Technology and Douglas Morrison of CERN high-energy physics lab near Geneva, Switzerland, who apparently took unseemly delight in puncturing each speaker's presentation with highly pointed questions.
And after three days of presentations and debate, an independent observer was left with several conclusions:
* That some new evidence has accumulated in the last year supporting the reality of cold fusion, particularly from the prestigious U.S. Department of Energy laboratories.
* That most observers outside the field are still not ready to accept that evidence.
* And that another year or two is going to be necessary for cold fusion to be either vindicated or finally discredited.
Fusion, which has been hailed as the energy source of the future for at least two decades, must normally be carried out at very high temperatures and pressures. Those conditions are essential to overcome the large repulsive forces that normally keep the nuclei of atoms separate.
Most fusion schemes involve isotopes of hydrogen, which normally has only a single proton in its nucleus, deuterium (which has a neutron as well) and radioactive tritium (which has two neutrons). In the most commonly considered reaction, two deuterium nuclei slam together at high speed, fusing into an unstable helium atom--helium-4--and releasing energy.
Pons and Fleischmann devised what they believe to be a clever way to get around the need for high temperatures and pressures. They knew that palladium metal (and some others) readily absorb hydrogen or deuterium, packing the atoms into the small spaces between metal nuclei.
They reasoned that application of a modest electrical field would increase the metal's absorption of deuterium from deuterium oxide (heavy water)--perhaps to the point where two deuterium nuclei would be forced into the space normally occupied by one. In that confined space, the repulsive forces between nuclei might be overcome and they would fuse, releasing energy.
And that is what they reported at their momentous press conference last March: that, over long periods of time, their simple electrochemical cell produced more energy than they put into it and, for brief periods, produced bursts of much more energy than they put into it.
That energy, they said, was much greater than could be accounted for by any known chemical process, and thus must be nuclear in origin. Unfortunately, their cell did not seem to produce any of the nuclear debris that should have been associated with a fusion reaction: no neutrons, no tritium, no detectable helium-3 and no significant radiation of any other sort.
This lack of nuclear debris, along with other labs' difficulty in reproducing their results, has been the primary stumbling block in persuading physicists to accept their conclusion.
By the time of the recent meeting, as many as 25 other laboratories around the world had reproduced Pons' and Fleischmann's discovery of heat production, including researchers at both the Los Alamos National Laboratory in New Mexico and the Oak Ridge National Laboratory in Tennessee. (But, Morrison and other critics argue repeatedly, perhaps another 250 have been unable to do so.)
Perhaps 15 of those labs, most notably chemist John O'M. Bockris' group at Texas A&M; University in College Station, have obtained substantial quantities of tritium in their experimental cells. Bockris says the Department of Defense has approached him about the possibility of producing tritium for nuclear weapons.
Some researchers, particularly at the Bhabha Atomic Research Center in Bombay, India, have also observed neutrons, gamma rays, and even X-rays emanating from the cells.
But, charge the critics, the amount of nuclear debris observed even in the best of experiments reported here is still orders of magnitude lower than the amount that should be present if the excess heat were caused by fusion.
"The reports here are very interesting," Petrasso said, "but there is nothing here to change my mind. They haven't addressed the fundamental issue: What are the end products? You have to have particles (nuclear debris) commensurate with the amount of heat produced, and they are not there."
That sentiment was echoed by chemist John R. Huizenga of the University of Rochester, who chaired a Department of Energy panel that last year recommended against providing funding for cold fusion research. "I don't see anything new here that wasn't available to us when we prepared that report. There is no reason to change one statement in it. There's a large discrepancy between the heat and the particles, and until they can explain it, it's not fusion."
Even cold fusion's firmest proponents are troubled about why more nuclear debris is not apparent. "I would like to know that too," said chemist Robert A. Huggins of Stanford University, who has been claiming excess heat production nearly as long as Fleischmann and Pons. "But there is so much favorable evidence that you have to be really stupid--don't use that word, it'll get me in trouble--not to believe something is happening."
The most important point is that there is at least some nuclear debris produced, added physicist Wilford Hansen of Utah State University in Logan, a member of the state advisory council that approved release of $4.5 million in state funds to the University of Utah group.
"By anybody's standards, we've had substantial proof that there are nuclear byproducts," Hansen said. "It's not required that anyone show enough to account for the heat."
Perhaps, said chemist Michael C. H. McKubre of SRI International in Palo Alto, the heat production is caused by a nuclear reaction that theoretical physicists have not yet discovered. "If experimental results don't match theory," he said, "then theory must change." Added Utah chemist Cheves Walling: "It's not up to us to explain it (the phenomenon). It's up to us to solidify the data and let nuclear physicists explain it."
Equally troubling to many critics is the general lack of reproducibility of results. Even at the labs that claim to have been successful in achieving cold fusion, success is often achieved in as few as 30% of experiments. "The phenomenon cannot be reproduced on demand," conceded physical chemist George G. Will, the ex-General Electric researcher who recently became head of the National Cold Fusion Institute here.
The one thing that is most needed now to persuade skeptics, according to physicist Howard Menlove of Los Alamos, "is a recipe that they can reproduce."
That recipe may soon be at hand, according to Pons. In an invitation-only press conference on the first day of the meeting, Pons said, "All of our experiments show excess heat"--a claim that he reduced in a formal presentation to 80%.
Pons and Fleischmann have been preparing a lengthy paper detailing their experimental procedures that will be published in the July Journal of Fusion Technology. "We can't put the issue of reproducibility to rest," Fleischmann said, "but we can put it to doze." Results of their search for nuclear debris will be published this fall in two other papers.
Meanwhile, the specter of a chemist who wasn't present at this meeting hovered in the wings. Glenn Schessow of the University of Florida in Gainesville has told colleagues and some members of the news media that he is able to turn cold fusion on and off at will in his laboratory, a feat that has eluded even Pons and Fleischmann.
Fleischmann has visited Schessow's laboratory for a demonstration and told the unofficial press conference that he was "very impressed." Schessow says he had been forbidden to talk about his results or to come to the meeting by his patent attorneys.
Ultimately, any final decision on the validity of the cold fusion phenomenon awaits the appearance of the now almost mystical recipe long-promised by the Utah researchers. "We'll publish our papers, and then we'll see," Pons said.